It is well known that some individuals are intolerant to lactose. Further, it may be desirable at certain times for individuals to avoid ingesting milk having a normal lactose content (about 4.6-4.9% w/v), particularly when the gastro-intestinal epithelium is momentarily compromised in its capacity to convert lactose to the monosaccharides glucose and galactose. Such situations occur, for example, when an individual is afflicted with diarrhea, gastroenteritis or a gastrointestinal disorder caused by the administration of antibiotics. When the affected individual is a nursing infant, it may be necessary to substitute the mother's milk with a lactose-free milk. A soy based milk, which does not naturally comprise lactose, is an acceptable alternative under circumstances where lactose intolerance occurs or where lactose is to be avoided for a given period of time. However, many individuals reduce or eliminate milk consumption because they dislike the taste of soy-based milk.
Different approaches exist to modify the composition of milk. Enzymatic processes used to eliminate lactose from milk are well known in the art. They usually comprise the step of adding lactase to milk for a time sufficient to convert lactose into monosaccharides. The major problem occurring with this type of process is that the production of monosaccharides increases the taste of the milk to an unacceptably sweet level.
U.S. Pat. No. 4,957,752 describes a process for making an ultrafiltrated milk which is used in the production of kefir. A partial delactosylation is achieved which reduces the ratio of lactose to protein from about 1.5:1 to about 1:1 (measured as percentages on a dry weight basis). This reference does not identify any undesirable modifications of the organoleptic properties of milk so delactosylated and further treated with a lactase, and consequently does not provide solutions for solving the problem arising from the action of lactase.
U.S. Pat. No. 4,956,186 describes a process for making yogurt. This process also comprises the steps of ultrafiltering milk and hydrolysing lactose with a lactase. Apparently the sweet taste of the resulting milk was not a concern in this reference, because a sugar substitute was added to the yogurt.
There is therefore a need for an improved process for preparing lactose-free milk. In particular, there is a need for a process resulting in lactose-free milk whose organoleptic properties are not negatively affected.